Copolyetheresters are well known and have enjoyed continued and increasing commercial success. They are available from several sources including the Hytrel.RTM. resins from E. I. duPont and the RITEFLEX resins from Celanese (formerly GAFLEX resins from GAF) and are described in U.S. Pat. Nos. 3,023,192; 3,651,014; 3,763,109; 3,766,146; 3,784,520; 3,801,547; 4,156,774; 4,264,761 and 4,355,155, among others. These copolyetheresters have a number of desirable properties including excellent tear strength, flex life, toughness, and general elastomeric stress-strain characteristics.
Dependent upon the application, there are various modulus and durometer requirements. To some extent these properties can be varied by the constituents of the polyetherester, but such "custom" synthesis can be costly and impractical when a wide range is required.
It has now been surprisingly found that effective amounts of the aforementioned multistage polymer modifier can be combined with a copolyetherester and a thermoplastic polyester and optionally a mineral filler thereupon obtaining moldable compositions exhibiting good modulus and tensile properties.
It is an object of the present invention to provide thermoplastic molding compositions which are suitable for a broad range of end use applications and providing molded parts with good physical integrity and stiffness.